Name-a-fallacy fallacy

The name-a-fallacy fallacy refers to the fallacy in which, rather than engaging with their opponent's arguments in detail, a person responds with the mention of a logical fallacy, without any explanation of how the fallacy actually applies to the argument at hand.

This fallacy is particularly common among atheists, although not exclusive to them. Here is an example of the fallacy in action:

Christian: Everything that begins to exist, must have a cause. The universe began to exist, therefore the universe must have a cause. And the cause of the universe, we call "God".

Atheist: That's special pleading.

The Christian may or may not be guilty of special pleading; but the atheist is definitely guilty of the name-a-fallacy fallacy, because they have made no effort to actually engage with the Christian's argument, or explain how it constitutes special pleading (if it in fact does). Knowledge of logical fallacies can be a useful tool, but they are not magical talismans which will defeat any argument simply by being mentioned; and yet, practitioners of the name-a-fallacy seem to think that they are exactly that.

In order to legitimately accuse your opponent of a logical fallacy, there are three necessary elements:

It is necessary to provide a clear definition of what the fallacy is. Many logical fallacies are defined in different ways by different people, and it is impossible to answer the subsequent two questions without a clear definition being adopted.

Reason to believe that the fallacy is actually a fallacy. A form of argument does not become fallacious merely by having the label "fallacy" attached to it; anyone who wishes to label something fallacious, needs to provide a clear and convincing argument that what they claim to be fallacious in fact actually is. Even if it is agreed that some instances of a particular type of argument are clearly fallacious, it does not automatically follow that all arguments of that type are necessarily fallacious; to hold so would be to potentially commit the fallacy of overgeneralization.

A clear and convincing explanation of why your opponent's argument is in fact an instance of that fallacy. One line answers have no place in serious debate.